What is drip Irrigation?
Drip Irrigation is the localized application of irrigation water to the crop. Drip irrigation systems save a lot of water. In drip irrigation systems, water is applied drop by drop through small holes called emitters. It can save up to 30-60% of water and can be used for almost all kind of orchards, row crops and vegetables.
Advantages of Drip Irrigation
- Saves 30-60% water
- Saves electricity and labor
- Uniform distribution of water
- Controlled application of soluble fertilizers
- Controls weeds and soil erosion
- Enable use of saline water
When to Use Drip Irrigation
Drip irrigation is sometimes called trickle irrigation and involves dripping water onto the soil at very low rates (2-20 liters/hour) from a system of small diameter plastic pipes fitted with outlets called emitters or drippers. Water is applied close to plants so that only part of the soil in which the roots grow is wetted, unlike surface and sprinkler irrigation, which involves wetting the whole soil profile. With drip irrigation water, applications are more frequent (usually every 1-3 days) than with other methods and this provides a very favorable moisture level in the soil in which plants can flourish.
Drip irrigation is most suitable for row crops (vegetables, soft fruit), tree and vine crops where one or more emitters can be provided for each plant. Generally, only high value crops are considered for drip irrigation because of the high capital costs of installing a drip system.
Drip irrigation is adaptable to any farmable slope. Normally the crop is planted along contour lines and the water supply pipes (laterals) are laid along the contour also. This is done to minimize changes in emitter discharge as a result of land elevation changes.
Drip irrigation is suitable for most soils. On clay soils water must be applied slowly to avoid surface water ponding and runoff. On sandy soils higher emitter discharge rates will be needed to ensure adequate lateral wetting of the soil.
Suitable irrigation water
One of the main problems with drip irrigation is blockage of the emitters. All emitters have very small waterways ranging from 0.2-2.0 mm in diameter and these can become blocked if the water is not clean. Thus it is essential for irrigation water to be free of sediments. If this is not so then filtration of the irrigation water is required prior to application.
Blockage may also occur if the water contains algae, fertilizer deposits and dissolved chemicals which precipitate such as calcium and iron. Filtration may remove some of the materials but the problem may be complex to solve and requires an experienced engineer or consultation with the equipment dealer.
Drip irrigation is particularly suitable for water of poor quality (saline water). Because drip irrigation forms a wetting front that reduces the salinity around the root and hence optimising the conditions suitable for growth. Beside this, gypsum powder is used in water tank to make saline water fit for irrigation in drip system.
Dripping water to individual plants means that the method can be very efficient in water use. For this reason, it is most suitable when water is scarce.
Drip System Layout
A typical drip irrigation system consists of the following components:
- Pump unit
- Control head
- Main and sub main lines (PVC)
- Laterals (PVC)
- Emitters or drippers
How Drip Irrigation Works:
The pump unit takes water from the source and provides the right pressure for delivery into the pipe system.
The control head consists of valves to control the discharge and pressure in the entire system. It may also have filters to clear the water. Common types of filter include screen filters and graded sand filters which remove fine material suspended in the water. Some control head units contain a fertilizer or nutrient tank. These slowly add a measured dose of fertilizer into the water during irrigation. This is one of the major advantages of drip irrigation over other irrigation methods.
Mainlines, sub main lines and laterals pipes supply water from the control head into the fields. They are usually made from PVC or polyethylene hose and should be buried below ground because they easily degrade when exposed to direct solar radiation. Lateral pipes are usually 13-32 mm diameter.
Emitters or drippers are devices used to control the discharge of water from the lateral pipes to the plants. They are usually spaced more than 1 meter apart with one or more emitters used for a single plant such as a tree. For row crops more closely spaced emitters may be used to wet a strip of soil. Many different emitter designs have been produced in recent years. The basis of design is to produce an emitter which will provide a specified constant discharge which does not vary much with pressure changes, and does not block easily.